1. Field of the Invention
This invention relates to a novel organic compound and more particularly it relates to a 2-substituted-alkyl ether having an optically active group and being useful as a component of ferroelectric liquid crystal compositions.
2. Description of the Related Art
At present, TN (twisted nematic) type display mode has been most broadly employed. This TN liquid crystal display mode has many advantages such as low driving voltage, small power consumption, etc., but it is inferior in the aspect of the response rate to emissive type display elements such as cathode-ray tube, electroluminescence, plasma display, etc. New TN type display elements having an increased twist angle up to 180.degree.-270.degree. have also been developed, but they are still inferior in the response rate. Efforts in various improvements have been made as described above, but a TN type display element having a high response rate has not yet been realized. However, a novel display mode using a ferroelectric liquid crystal which has recently been extensively researched has a possibility that the response rate is notably improved (Clark et al, Applied Phys. lett., 36, 899 (1980)). This mode utilizes chiral smectic phases exhibiting ferroelectricity such as chiral smectic C phase (hereinafter abbreviated to SC*). Phases exhibiting ferroelectricity are not limited to SC* phase, but it has been known that phases of chiral smectic F, G, H, I, etc. also exhibit ferroelectricity.
Various characteristics are required for terroelectric liquid crystal materials to be practically used for ferroelectric liquid crystal display elements, but at present there is no single compound which satisfies these characteristics; hence it is necessary to use ferroelectric liquid crystal compositions obtained by blending some liquid crystal compounds or non-liquid crystalline compounds.
Further, not only ferroelectric liquid crystal compositions consisting only of ferroelectric liquid crystal compounds are used, but also Japanese patent application laid-open No. Sho 60-36003 discloses that compounds or compositions exhibiting phases of achiral smectic C, F, G, H, I, etc. (hereinafter abbreviated to phases of SC, etc.) as basic substances can be blended with one or more kinds of compounds exhibiting ferroelectric liquid crystalline phases, whereby it is possible to make up the whole into a ferroelectric liquid crystal composition. Further, a report discloses that by blending compounds or compositions exhibiting phases of SC, etc. as basic substances with one or more kinds of compounds which are optically active but exhibit no ferroelectric liquid crystalline phase, it is possible to make up the whole into a ferroelectric liquid crystalline composition (Mol. Liq. Cryst., 89, 327 (1982)).
When these facts are summarized, it is seen that by blending one or more kinds of optically active compounds, irrespective of whether or not these compounds exhibit ferroelectric liquid crystalline phases, with basic substances, it is possible to constitute a ferroelectric liquid crystal composition. However, the optically active substances are preferred to exhibit liquid crystalline phases, and even when they exhibit no liquid crystalline phases, their structures are preferred to be similar to those of liquid crystal compounds, so to speak, quasi liquid crystalline substances.